The Siberian Husky owes its characteristic blue eyes in part to a genetic mutation identified with help from a consumer DNA test.
In the largest canine study of its kind, Adam Boyko and Aaron Sams of Embark Veterinary in Boston, Massachusetts, and their colleagues analysed DNA and other information collected by the owners of more than 3,100 dogs of various breeds. Blue eyes were generally rare for most breeds, but in 75% of the blue-eyed animals, the team found a duplicated stretch of DNA on chromosome 18.
By contrast, this sequence rarely appeared in the genomes of brown-eyed dogs. The duplication occurred near ALX4, a gene that is important in mammalian eye development. Analysis of nearly 3,000 more dogs confirmed a strong association between the mutation and blue eyes.
In Siberian Huskies, a single copy of the duplication seemed sufficient to cause blue eyes in most animals. In other breeds, however, some animals with a single copy had brown eyes, suggesting that other genetic factors can interact with the duplication's effect on eye colour.